A Polysiloxide Complex with two Chromium(III) η2-Superoxo Moieties

The isolation and identification of intermediates formed in the course of the activation of dioxygen at transition metal centers reveals important mechanistic insights concerning such processes. We previously reported the reaction of the dinuclear Cr^II complex [L₂Cr₂(MeCN)₂][Li(MeCN)]₂ (L=PhSi(OSiPh₂O⁻)₃) ( 5 ) with dioxygen, which resulted in the formation of the Cr^IV oxo complex [L₂Cr₂O₂][Li(THF)₂]₂ ( 6 ), as the final room temperature stable product. Here we now report the isolation and characterization of an intermediate en route to 6 , namely the dinuclear Cr^III superoxo complex [L₂Cr₂(O₂)₂][Li(MeCN)]₂ ( 7 ). 7 is the first example of a structurally characterized dinuclear Cr^III superoxo complex with two independent side-on bound superoxo ligands. Reactivity studies outline the capability of this superoxo complex to activate weak O−H bonds.     

Characterization of seasonal variation of forest canopy in a temperate deciduous broadleaf forest, using daily MODIS data

In this paper, we present an improved procedure for collecting no or little atmosphere- and snow-contaminated observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. The resultant time series of daily MODIS data of a temperate deciduous broadleaf forest (the Bartlett Experimental Forest) in 2004 show strong seasonal dynamics of surface reflectance of green, near infrared and shortwave infrared bands, and clearly delineate leaf phenology and length of plant growing season. We also estimate the fractions of photosynthetically active radiation (PAR) absorbed by vegetation canopy (FAPAR_canopy), leaf (FAPAR_leaf), and chlorophyll (FAPAR_chl), respectively, using a coupled leaf-canopy radiative transfer model (PROSAIL-2) and daily MODIS data. The Markov Chain Monte Carlo (MCMC) method (the Metropolis algorithm) is used for model inversion, which provides probability distributions of the retrieved variables. A two-step procedure is used to estimate the fractions of absorbed PAR: (1) to retrieve biophysical and biochemical variables from MODIS images using the PROSAIL-2 model; and (2) to calculate the fractions with the estimated model variables from the first step. Inversion and forward simulations of the PROSAIL-2 model are carried out for the temperate deciduous broadleaf forest during day of year (DOY) 184 to 201 in 2005. The reproduced reflectance values from the PROSAIL-2 model agree well with the observed MODIS reflectance for the five spectral bands (green, red, NIR₁, NIR₂, and SWIR₁). The estimated leaf area index, leaf dry matter, leaf chlorophyll content and FAPAR_canopy values are close to field measurements at the site. The results also showed significant differences between FAPAR_canopy and FAPAR_chl at the site. Our results show that MODIS imagery provides important information on biophysical and biochemical variables at both leaf and canopy levels.     

Characterization of human gamma 4 switch region polymorphisms suggests a meiotic recombinational hot spot within the Ig locus: influence of S region length on IgG4 production

Human gamma4 gene RFLPs, revealed after BamHI digestion, show IGHG4 alleles of 9.0 (9.2), 9.4, and 9.6 kb at various frequencies in different ethnic populations. Studies in immunodeficient individuals have previously suggested that the 9.4 BamHI allele is associated with a higher serum level of IgG4 than the 9.0 (9.2) BamHI allele, but it is not clear whether this is associated with the S region itself or other control elements. In addition, a duplication of the 9.4-kb gamma4 allele has recently been observed in a high proportion of normal donors. We therefore undertook a study of the structural basis for the difference in Ab levels in the various gamma4 alleles. We demonstrate that the Sgamma4 alleles differ in length due to deletions and insertions of a varying number of 79-bp Sgamma4 repeat units. Two novel RFLPs, 8.8 and 9.1 kb, were also observed. The alleles are likely to be generated by unequal crossing over, and the breakpoints cluster in Sgamma4 repeat units that contain chi-like motifs, implicating chi-like sequences in the meiotic recombination. Our data support the idea that the 9.4-kb BamHI allele is more productive than the 9.0 (9.2)-kb allele in normal healthy donors, possibly due to the extended switch regions, whereas duplication of the gamma4 gene has no effect on switching and IgG4 serum levels.     

A novel gene expressed in rat ameloblasts codes for proteins with cell binding domains

Two variants of an mRNA sequence are identified that are expressed at high levels in rat ameloblasts during the formation of the enamel matrix. The sequences contain open reading frames for 407 and 324 amino acid residues, respectively. The encoded proteins, which we call amelins, are rich in proline, glycine, leucine, and alanine residues and contain the peptide domain DGEA, an integrin recognition sequence. The sequences coding for the C-terminal 305 amino acid residues, the 3' nontranslated part, and a microsatellite repeat at the nontranslated 5' region are identical in both mRNA variants. The remaining 5' regions contain 338 nucleotides unique to the long variant, 54 common nucleotides, and 46 nucleotides present only in the short variant. Eleven nucleotides have the potential to code for 5 amino acids of both proteins in different reading frames. The reading frame of the longer variant includes codons for a typical N-terminal signal peptide. The amelins are likely to be constituents of the enamel matrix and the only proteins that have so far been implicated in binding interactions between the ameloblast surface and its extracellular matrix.     

Factors predictive of bile duct stones in patients with acute calculous cholecystitis

A 13-month-old girl developed opsoclonus-myoclonus syndrome in association with neuroblastoma. She showed irritability, hyperhidrosis and a bad temper. Serum and urinary vanilmandelic acid, homovanilic acid and catecholamines were elevated at the same time. Chest CT demonstrated the presence of neuroblastoma in the paravertebral region. Cranial CT and MRI revealed no abnormal findings. Brainstem auditory-evoked potentials and short latency somatosensory evoked potentials were normal, whereas blink reflex showed long duration and high amplitude of late components (R2 and R2') indicating hyperexcitability of the interneurons in the lower brainstem. These findings improved gradually as opsoclonus disappeared. Her neurologic symptoms resolved completely within 2 years after the resection of the tumor. The hyperexcitability of the blink reflex may indicate the hyperactivity of the neurons in the brainstem reticular formation responsible for the abnormal saccadic eye movements (opsoclonus), which could be caused by the oversecretion of dopamine or by the supersensitivity of dopaminergic receptors.     

Detection of muramidase (lysozyme)-secreting leucocytes at the single-cell level by a protein A plaque assay

Using a modification of the protein A plaque assay, muramidase (lysozyme)-producing leucocytes were detected as plaque-forming cells. In the presence of anti-muramidase Ig and complement the secreted lysozyme resulted in lysis of protein-A-coated target erythrocytes. By the use of a monolayer technique individual plaque-forming cells could be identified by staining procedures. Granulocytes as well as monocytes were found to produce muramidase and thus to form plaques. This method could serve as a useful tool when studying lysozyme secretion. Furthermore, by the use of appropriate antisera, this method could be employed for the study of any cell type (any secretion), provided enough molecules are being secreted.     

Factors predictive of early complications of endoscopic treatment of bile duct calculi

BACKGROUND/AIMS: Factors associated with an increased early complication rate of the endoscopic sphincterotomy procedure have been identified. Precut or needle knife papillotomy has been shown to improve the success rate of endoscopic retrograde cholangiography and endoscopic sphincterotomy, but has often been reported to be hazardous. In order to identify patients with bile duct stones at risk for a complicated course in connection with endoscopic clearance of the calculi, factors predictive of early complications were sought. METHODOLOGY: 417 consecutive patients with bile duct calculi at endoscopic retrograde cholangiography were considered for endoscopic treatment in our department from 1981 to 1992. Endoscopic sphincterotomy was performed in 246 patients with intact gallbladders and in 147 with prior cholecystectomy, 55 of whom had retained calculi. RESULTS: There was a 9.4% overall and 7.1% major early complication rate of the EST procedure and a 30-day mortality of 0.5% (2 patients, non-procedure related). In 22% (6/27) of the patients with major complications, surgery was required or preferred to additional endoscopic measures. Complete stone removal failed in 35/393 patients (8.9%). The immediate and early complication rate of standard sphincterotomy was not found to be increased in patients with prior or present biliopancreatic complications, failed bile duct clearance at first attempt, or juxtapapillary diverticula. It was the same after standard sphincterotomy as after precut papillotomy followed by immediate or delayed sphincterotomy. No increased morbidity was found after failed therapy as compared to failed diagnostic precut papillotomy. There was neither a greater need for, nor an increased complication rate following, precut papillotomy in patients with, as compared to those without, juxtapapillary diverticula. Endoscopic experience did not influence the complication rate. There were no significant differences regarding outcome or risk factors associated morbidity between patients with and without intact gallbladder. CONCLUSIONS: These findings confirm that endoscopic treatment is safe and that precut papillotomy can be performed without increased morbidity. Furthermore, none of the commonly identified factors associated with increased morbidity were found to be risk factors in this study.